William eats at a cafe and the cost of his meal is $\$31.00$. He would like to leave a $15\%$ tip. What is his total bill including tip?
Answer: The tip amount is equal to $15\% \times \$31.00$ We can find the tip by first calculating a $10\%$ tip and a $5\%$ tip, and then adding those two numbers together. To calculate a $10\%$ tip, move the decimal point in $\$31.00$ one place to the left. $10\%$ $\times \$31.00$ $\$3.10$ To calculate a $5\%$ tip, divide the $10\%$ tip amount in half. $5\%$ $\times \$31.00 = $ $\$3.10$ $ \div 2 = $ $\$1.55$ Adding the two amounts together gives us $\$3.10$ $\$1.55 =$ $ \$4.65$ The cost of the meal plus the amount of the tip will equal the total bill amount. $\$31.00 + \$4.65 = $ $\$35.65$ The total cost of the bill is $\$35.65$.